Far-infrared detector based on HgTe/HgCdTe superlattices

HgTe/Hg0.05Cd0.95Te superlattices (SLs) were grown on (112)B oriented Cd0.96Zn0.04Te substrates using molecular beam epitaxy (MBE). The SLs, consisting of 100 periods of 80-Angstrom-thick HgTe wells alternating with 77-Angstrom-thick Hg0.05Cd0.95Te barriers, were designed to operate as detectors in the far-infrared (FIR) region. Infrared absorption spectroscopy, high-resolution transmission electron microscopy (TEM), Hall effect measurements, and x-ray diffraction were used to characterize the superlattice layers. A series of annealing experiments were initiated to quantify the temperature-dependent interdiffusion of the HgTe wells and Hg0.05Cd0.95Te barriers and consequently their degradation, which shifts the absorption edges of the SLs to higher energies, since a high-temperature ex situ anneal is normally required in order to produce the p-type material required for a photovoltaic detector. Results from infrared absorption spectroscopy, TEM, and Hall effect measurements for the annealed samples are presented. A FIR SLs single-element photoconductive (PC) device was designed and fabricated. Both material characterization and device testing have established the applicability of the HgTe/Hg0.05Cd0.95Te SLs for the FIR region.